hw/9pfs: Add open flag mapping

Some of the flags are OS/arch dependent we need to use
9P defined value on wire,

Based on the original patch from Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
diff --git a/hw/9pfs/virtio-9p.h b/hw/9pfs/virtio-9p.h
index e5cf78c..e94041e 100644
--- a/hw/9pfs/virtio-9p.h
+++ b/hw/9pfs/virtio-9p.h
@@ -352,6 +352,30 @@
     V9fsString fullname;
 } V9fsMkState;
 
+/* 9p2000.L open flags */
+#define P9_DOTL_RDONLY        00000000
+#define P9_DOTL_WRONLY        00000001
+#define P9_DOTL_RDWR          00000002
+#define P9_DOTL_NOACCESS      00000003
+#define P9_DOTL_CREATE        00000100
+#define P9_DOTL_EXCL          00000200
+#define P9_DOTL_NOCTTY        00000400
+#define P9_DOTL_TRUNC         00001000
+#define P9_DOTL_APPEND        00002000
+#define P9_DOTL_NONBLOCK      00004000
+#define P9_DOTL_DSYNC         00010000
+#define P9_DOTL_FASYNC        00020000
+#define P9_DOTL_DIRECT        00040000
+#define P9_DOTL_LARGEFILE     00100000
+#define P9_DOTL_DIRECTORY     00200000
+#define P9_DOTL_NOFOLLOW      00400000
+#define P9_DOTL_NOATIME       01000000
+#define P9_DOTL_CLOEXEC       02000000
+#define P9_DOTL_SYNC          04000000
+
+/* 9p2000.L at flags */
+#define P9_DOTL_AT_REMOVEDIR         0x200
+
 /* 9P2000.L lock type */
 #define P9_LOCK_TYPE_RDLCK 0
 #define P9_LOCK_TYPE_WRLCK 1